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The International Space Station (ISS) is a large space station assembled and maintained in low Earth orbit by a collaboration of five space agencies and...

A star is a luminous spheroid of plasma held together by self-gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked...

The expansion of the universe is the increase in distance between gravitationally unbound parts of the observable universe with time. It is an intrinsic...

The angular diameter, angular size, apparent diameter, or apparent size is an angular distance describing how large a sphere or circle appears from a given...

99942 Apophis (provisional designation 2004 MN4) is a near-Earth asteroid and a potentially hazardous object with a diameter of 370 metres (1,210 feet)...

The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and...

The dwarf planet Pluto has five natural satellites. In order of distance from Pluto, they are Charon, Styx, Nix, Kerberos, and Hydra. Charon, the largest...

Interstellar travel is the hypothetical travel of spacecraft from one star system, solitary star, or planetary system to another. Interstellar travel is...

Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. In-space propulsion exclusively deals with propulsion systems...

The Moon orbits Earth in the prograde direction and completes one revolution relative to the Vernal Equinox and the stars in about 27.32 days (a tropical...

The solar eclipse of August 21, 2017, dubbed the "Great American Eclipse" by some media, was a total solar eclipse visible within a band that spanned the...

NASA's series of Great Observatories satellites are four large, powerful space-based astronomical telescopes launched between 1990 and 2003. They were...

A total solar eclipse occurred at the Moon's descending node of the orbit on Wednesday, July 22, 2009, with a magnitude of 1.07991. It was the longest...

Hertzsprung–Russell diagram Spectral type O B A F G K M L T Brown dwarfs White dwarfs Red dwarfs Subdwarfs Main sequence ("dwarfs") Subgiants Giants Red...

Discovery and exploration of the Solar System is observation, visitation, and increase in knowledge and understanding of Earth's "cosmic neighborhood"...

A total solar eclipse occurred on Saturday, March 7, 1970, visible across most of North America and Central America. A solar eclipse occurs when the Moon...

Adirondack is the nickname for Mars Exploration Rover Spirit's first target rock.[citation needed] Scientists chose Adirondack to be Spirit's first target...

Apollinaris Mons is an ancient shield volcano in the southern hemisphere of Mars. It is situated near the equator, south of Elysium Planitia and north...

Mars 96 (sometimes called Mars-8) was a failed Mars mission launched in 1996 to investigate Mars by the Russian Space Forces and not directly related to...

An eyeball planet is a hypothetical type of tidally locked planet, for which tidal locking induces spatial features (for example in the geography or composition...